Because the base OS needs to be something an admin can work comfortably on, esp. if the host is supposed to run other things besides docker (e.g. a database, you do not want to run mysql over a network if possible).

And for this you need a "real" base OS, which will be either apt-flavor (debian/ubuntu) or rpm-flavor (rhel, sles), depending on the organization.

Why not run your database on a different machine then. Separation of concerns. Have a cluster a machines for containers so you can take advantage of it's strengths instead of trying to duct tape everything together on machine

> Why not run your database on a different machine then. Separation of concerns.

While true in general, you always end up introducing latency (simply because it's on a different host) and possible packet losses/retransmits (e.g. when the switch buffer memory overruns). Given the "hft" in the blog name (high-speed financial transactions), both can equal losses of money.